Process for preparing oxime containing silicon compounds

ABSTRACT

A process for preparing oxime containing silicon compounds which comprises reacting an oxime with a silicon compound having at least three nitrogen atoms linked to the same silicon atom through Si--N bonding per molecule.

The present invention relates to oxime containing silicon compounds andmore particularily to a process for preparing oxime containing siliconcompounds by reacting oximes with silicon compounds having at leastthree nitrogen atoms bonded to the same silicon atom through Si--Nbonding per molecule.

BACKGROUND OF THE INVENTION

Heretofore oxime containing silicon compounds have been prepared byreacting silicon compounds having Si-halogen bonds with oximes,preferably in the presence of acid acceptors, such as triethylamine,pyridine, alpha-picoline or mixtures thereof. (See U.S. Pat. No.3,674,738.)

In comparison to the process described in the above cited patent, theprocess of this invention has certain advantages. For example, thereaction proceeds at a rapid rate and excellent yields of desiredproduct are obtained in the absence of expensive acid acceptors.

Therefore, it is an object of this invention to provide a process forpreparing oxime containing silicon compounds. Another object of thisinvention is to provide a process for preparing oxime containing siliconcompounds in the absence of acid acceptors. A further object of thisinvention is to provide a process for preparing oxime containing siliconcompounds by reacting oximes with silicon compounds having at leastthree nitrogen atoms bonded to the same silicon atom through Si--Nbonding per molecule.

SUMMARY OF THE INVENTION

The foregoing objects and others which will become apparent from thefollowing description are accomplished in accordance with thisinvention, generally speaking, by providing a process for preparingoxime containing silicone compounds which comrises reacting oximes withsilicon compounds having at least three nitrogen atoms linked to thesame silicon atom through Si--N bonding per molecule at a temperature offrom about 0° C. up to about 150° C.

DETAILED DESCRIPTION OF INVENTION

Oximes which have been employed heretofore in the reaction with siliconcompounds having Si-bonded halogen atoms, especially Si-bonded chlorineatoms, may be used in the process of this invention. These oximes can berepresented by the general formula:

    HON═X

in which X is ═CRR¹ or ═CR² , R represents a monovalent or a substitutedmonovalent hydrocarbon radical, R¹ is hydrogen or the same as R and R²represents a bivalent or a substituted bivalent hydrocarbon radical.

Examples of hydrocarbon radicals represented by R and R¹ are alkylradicals, such as the methyl, ethyl, n-propyl, isopropyl, n-butyl andsec-butyl radical as well as octadecyl radicals; alkenyl radicals, suchas the vinyl and allyl radical; saturated cyclo-aliphatic hydrocarbonradicals such as the cyclopentyl and cyclohexyl radical, as well asmethylcylohexyl radicals; cycloaliphatic hydrocarbon radicals havingcarbon-carbon multiple bonds, such as the cyclohexenyl radical; arylradicals such as the phenyl radical, as well as the xenyl and naphthylradicals; aralkyl radicals such as the benzyl, beta-phenylethyl andbeta-phenylpropyl radical and alkaryl radicals such as the tolylradicals.

Examples of preferred substituted hydrocarbon radicals represented by Rand R¹ are perfluoralkylethyl radicals such as the 3,3,3-trifluoropropylradicals and haloaryl radicals such as chlorophenyl radicals andcyanoalkyl radicals such as the beta-cyanoethyl radicals.

Examples of R² radicals, i.e. bivalent, or substituted bivalenthydrocarbon radicals which form a ring with the carbon atom of the C═ONgroup, are those of the following formulas:

    --CH.sub.2 (CH.sub.2).sub.3 CH.sub.2 --

    --ch.sub.2 (ch.sub.2).sub.4 ch.sub.2 --

    --c.sub.6 h.sub.4 c.sub.6 h.sub.4 --

    --ch.sub.2 [c(ch.sub.3).sub.2 ]ch.sub.2 ch.sub.2 -- ##STR1## and hydrocarbon radicals which are substituted by halogen, namely those having the following formulas:

    --CH.sub.2 CHCl(CH.sub.2).sub.3 --

    --c.sub.6 h.sub.4 c.sub.6 h.sub.3 br--

    --CF.sub.2 (CF.sub.2).sub.3 CF.sub.2 --

    --ch.sub.2 ch.sub.2 [c(ccl.sub.3).sub.2 ]CH.sub.2 --.

mixtures of various oximes may also be employed.

The silicon compounds used in accordance with this invention in which atleast three Si--N bonds are bonded to the same silicon atom, may containone or more silicon atoms per molecule. Silicon compounds having asilicon atom with at least three nitrogen atoms bonded thereto arepreferably those of the formula:

    R.sub.a Si(NR.sub.2.sup.1).sub.4-a,

where R and R¹ are the same as above and a is zero or 1.

It is preferred that the silicon compounds which contain more than onesilicon atom per molecule and have at least three nitrogen atoms linkedto one silicon atom through Si--N bonding, have from 2 to 22 siliconatoms per molecule. Moreover, it is preferred that the silicon compoundswhich contain more than one silicon atom per molecule and have threenitrogen atoms bonded to one silicon atom through Si--N bonding, thatthe silicon valences which are satisfied by substituents other thannitrogen and monovalent or substituted monovalent hydrocarbon radicals,be saturated with siloxane-oxygen atoms or bivalent hydrocarbonradicals.

The following formulas represent silicon compounds containing more thanone silicon atom per molecule in which at least three nitrogen atoms arebonded to the same silicon atom through Si--N bonding: ##STR2##

    R.sub.3 SiO(R.sub.2 SiO).sub.n Si(NR.sub.2.sup.1).sub.3,

    (R.sub.2.sup.1 N).sub.3 SiO(R.sub.2 SiO).sub.n Si(NR.sub.2.sup.1).sub.3 ,

    r.sub.3 si(CH.sub.2).sub.2 Si(NR.sub.2.sup.1).sub.3 and

    (R.sub.2.sup.1 N).sub.3 Si(CH.sub.2).sub.2 Si(NR.sub.2.sup.1).sub.3.

in the above formulas, R and R¹ are the same as defined above and n iszero or represents an integer of from 1 to 20.

Examples of substituted and unsubstituted hydrocarbon radicalsrepresented by R and R¹ in the oximes are, with the exception of thevinyl radical in the case of nitrogen bonded R and R¹ radicals, equallyapplicable to the substituted and unsubstituted hydrocarbon radicalsrepresented by R and R¹ in the above represented formulas for siliconcompounds having at least three nitrogen atoms linked to the samesilicon atom through Si--N bonding. Additional examples of nitrogenbonded radicals R and R¹ are the tert-butyl radical, the3,5,5-trimethylcyclohexyl radical and the 2,3,4-triethylcyclohexylradical.

Mixtures of various silicon compounds may be employed as well.

It is now possible with the process of this invention to prepare siliconcompounds in which only a portion of the original Si--N bonds issubstituted by SiON═C bonds, by using less than one mol of oxime foreach gram-atom of Si-bonded nitrogen. However it is also possible toprepare silicon compounds in which all of the original Si--N bonds arereplaced by SiON═C bonds, by reacting at least one mol and preferably 1to 2 mols of oxime per gram-atom of Si-bonded nitrogen. Thus, theprocess of this invention now makes it possible to prepare siliconcompounds having oxime groups which are bonded to silicon via oxygen, inaccordance with the following formula:

    R.sub.a Si(NR.sub.2.sup.1).sub.b (ON═X).sub.4-a-b,

where R, R¹ X and a are the same as above, b is zero, 1, 2 or 3, withthe provisio that the sum of a + b can be no greater than 3, whensilicon compounds having the following general formula are

    R.sub.a Si(NR.sub.2.sup.1).sub.4-a.

The process of this invention is preferably carried out at temperaturesof from 0° to 150° C. and more preferably from 15° to about 50° C. Also,it is preferred that the process be conducted at atmospheric pressure,i.e., at 760 mm Hg (abs.) or approximately 760 mm Hg (abs.). However isdesired, the process may be conducted either at lower or higherpressures.

It is preferred that the process be performed under anhydrousconditions; however the exculsion of water is not essential where theformation of oligomer products does not cause any problems.

One of the advantages of the process of this invention is that the useof inert solvents is not essential; however, they may be used ifdesired. Examples of suitable inert solvents which may be used in thisprocess are hydrocarbons such as petroleum ether, benzene and toluene;esters such as ethyl acetate; ethers such as diethyl ether, di-n-butylether, dioxane and tetrahydrofuran; ketones such as acetone; chlorinatedhydrocarbons such as methylene chloride; as well ashexamethyldisiloxane.

The process may be conducted batchwise, continuously orsemi-continuously.

The excess oxime as well as the ammonia or the amine formed during thereaction of the oxime with a silicon-bonded group of the formula NR₂ ¹can easily be removed by distillation at atmospheric or belowatmospheric pressure, so that a pure product can be easily obtained.

The silicon compounds having oxime groups bonded to silicon via oxygenwhich are obtained from the process of this invention may be used ascross-linking agents in the preparation of compositions which can bestored under anhydrous conditions, but cure to elastomers when exposedto water at room temperature. These curable compositions are prepared bymixing diorganopolysiloxanes containing condensable terminal groups withthe oxime containing cross-linking agents of this invention.

EXAMPLES 1 through 10

In each of the following examples one mol of silane is mixed with theoxime and the mixture so obtained is stirred for 3 hours at 30° C. underanhydrous conditions. Subsequently the volatile components of thereaction mixture are distilled off at 10 to 20 mm Hg (abs.) and at abath temperature of from 100° to 120° C. The distillation residue hasthe formula and the physical properties indicated in the Table. Theformulas representing the silane products obtained from the reaction arerepresented as average values. The yield is based on the silane used inthe reaction. In the formulas "C₆ H₁₁ " refers to the cyclohexylradical.

EXAMPLE 11

(a) In order to determine the reaction speed,methyltris-(cyclohexylamino)-silane is mixed in a Nuclear MagneticResonance tube with methyl-ethylketoxime at a ratio of 1 mol of silaneto 4 mols of oxime. After 5 minutes all NMR aminosilane signals havedisappeared and only the methyl proton signal from the puremethyltris-(methyl-ethylketoxime)silane can be detected. It is thus avery quick and quantitative reaction.

(b) In order to determine the location of the equilibrium in thereaction pursuant to this invention:

    .tbd.SiN═+HON═X → .tbd.SiON═X+HN═

methyltris-(methylethylketoxime)-silane is mixed with cyclohexylamine inthe ratio of one mol of silane to two mols of amine and heated to 60° C.After 7 days of heating at 60° C., gas chromatographic analysis does notreveal that any aminosilane or aminoximosilane have formed. It thusappears that the equilibrium is located entirely on the right hand sideof the above reaction equation, so that it is not necessary to removethe amine or ammonia during the reaction.

                                      TABLE                                       __________________________________________________________________________    Exam-                                                                         ple                        Oxime                     Yield                                                                             Physical             No. Silane     Oxime       Mol Product               %   Properties           __________________________________________________________________________    1   CH.sub.3 Si(NHC.sub.6 H.sub.11).sub.3                                                    HON=C(CH.sub.3)C.sub.2 H.sub.5                                                            1.5 CH.sub.3 Si(NHC.sub.6 H.sub.11).sub.1.5                                       [ON=C(CH.sub.3)C.sub.2 H.sub.5 ].sub.1.5                                                            99  n.sub.D.sup.25                                                                =1.4687              2   CH.sub.3 Si(NHC.sub.6 H.sub.11).sub.3                                                    HON=C(CH.sub.3)C.sub.2 H.sub.5                                                            4   CH.sub.3 Si[ON=C(CH.sub.3)C.sub.2 H.sub.5                                     ].sub.3               95  n.sub.D.sup.25                                                                =1.436               3   CH.sub.3 Si(NHC.sub.6 H.sub.11).sub.3                                                    HON=C(CH.sub.3).sub.2                                                                     2   CH.sub.3 SiNHC.sub.6 H.sub.11 [ON=C(CH.sub.                                   3).sub.2 ].sub.2      98  n.sub.D.sup.25                                                                =1.4661              4   CH.sub.3 Si(NHC.sub.6 H.sub.11).sub.3                                                    HON=C(CH.sub.3).sub.2                                                                     3.5 CH.sub.3 Si[ON=C(CH.sub.3).sub.2 ].sub.3                                                            96  n.sub.D.sup.25                                                                =1.4568              5   CH.sub.3 Si(NHsec-C.sub.4 H.sub.9).sub.3                                                 HON=C(CH.sub.3)C.sub.2 H.sub.5                                                            2   CH.sub.3 SiNHsec-C.sub.4 H.sub.9 [ON=C(CH.s                                   ub.3)C.sub.2 H.sub.5 ].sub.2                                                                        98  n.sub.D.sup.25                                                                =1.4460              6   C.sub.6 H.sub.5 Si(NHC.sub.6 H.sub.11).sub.3                                             HON=C(CH.sub.3)C.sub.2 H.sub.5                                                            1.5 C.sub.6 H.sub.5 Si(NHC.sub.6 H.sub.11).sub.                                   1.5 [ON=C(CH.sub.3)C.sub.2 H.sub.5                                            ].sub.1.5             99  n.sub.D.sup.25                                                                =1.5119              7   C.sub.6 H.sub.5 Si(NHC.sub.6 H.sub.11).sub.3                                             HON=C(CH.sub.3)C.sub.2 H.sub.5                                                            4   C.sub.6 H.sub.5 Si[ON=C(CH.sub.3)C.sub.2                                      H.sub.5 ].sub.3       99  n.sub.D.sup.25                                                                =1.5016              8   C.sub.2 H.sub.3 Si(NHC.sub.6 H.sub.11).sub.3                                             HON=C(CH.sub.3)C.sub.2 H.sub.5                                                            1.5 C.sub.2 H.sub.3 Si(NHC.sub.6 H.sub.11).sub.                                   1.5 [ON=C(CH.sub.3)C.sub.2 H.sub.5                                            ].sub.1.5             94  n.sub.D.sup.25                                                                =1.4772              9   C.sub.2 H.sub.3 Si(NHC.sub.6 H.sub.11).sub.3                                             HON=C(CH.sub.3)C.sub.2 H.sub.5                                                            4   C.sub.2 H.sub.3 Si[ON=C(CH.sub.3)C.sub.2                                      H.sub.5 ].sub.3       96  n.sub.D.sup.25                                                                =1.4649              10  Si(NHsec-C.sub.4 H.sub.9 ).sub.4                                                         HON=C(CH.sub.3)C.sub.2 H.sub.5                                                            5   Si[ON=C(CH.sub.3)C.sub.2 H.sub.5 ].sub.4                                                            99  Fp. =65°      __________________________________________________________________________                                                             C                

What is claimed is:
 1. A process for preparing oxime containing silicon compounds which comprises reacting an oxime with a silicon compound having at least three nitrogen atoms linked to the same silicon atom of said compound through Si--N bonding at a temperature of from about 0° to 150° C.
 2. The process of claim 1, wherein the oxime is reacted with the silicon compound in a ratio of one mol of oxime for each gram atom of Si-bonded nitrogen.
 3. The process of claim 1, wherein the reaction is conducted at a temperature of from 15° to 50° C.
 4. The process of claim 1, wherein the oxime has the formula

    HON═X,

in which X is selected from the group consisting of CRR¹ and CR², R is selected from the group consisting of monovalent hydrocarbon radicals and substituted monovalent hydrocarbon radicals, R¹ is selected from the group consisting of hydrogen and R, and R² is selected from the group consisting of bivalent hydrocarbon radicals and substituted bivalent hydrocarbon radicals.
 5. The process of claim 1, wherein the silicon compound has the formula

    R.sub.a Si(NR.sub.2.sup.1).sub.4-a,

in which R is selected from the group consisting of monovalent hydrocarbon radicals and substituted monovalent hydrocarbon radicals, R¹ is selected from the group consisting of hydrogen and R and a is 0 or
 1. 